[AstroPy] time conversion between JD and UT

Tim Jenness tim.jenness at gmail.com
Thu Sep 4 10:54:55 EDT 2014


On Thu, Sep 4, 2014 at 4:59 AM, gonghang.naoc <ghang.naoc at gmail.com> wrote:

> Hi all,
> I am trying astropy.time to do conversion between JD and UT.
> It is easier to convert UT to JD.  It seems JD equals jd1+jd2, right?  I
> do not know why there are two parts since one value is enough.
>

There are two values to allow you use high precision. A single double
precision number can not provide you with nanosecond precision as a JD. If
you split the JD into two distinct numbers (apportioned in a way that best
suits your requirements) you can retain accuracy.

-- 
Tim Jenness
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